Polynuclear croconato-bridged-copper(II) complexes derived from tri- and tetra-dentate amines

Three new polynuclear bridged croconato copper(II) complexes with different dimensionality {[Cu(bedmpza)(μ2-C5O5)]·4H2O}n (1), {[Cu3(aepn)3(μ2-C5O5)(μ3-C5O5)(H2O)](ClO4)2·1.6H2O}n (2), and [Cu2(dppa)2(μ2-C5O5)](ClO4)2·2H2O (3) where bedmpza = bis(2-(3,5-dimethylpyrazol-1-yl)ethyl)amine, aepn = N-(2-aminoethyl)-1,3-propanediamine, dppa = N-propionamide-N,N-bis(2-pyridylmethyl)amine, and C5O52− = the croconate dianion were synthesized and structurally characterized by single crystal X-ray crystallography. In these complexes, the bridged croconato ligand displays a variety of coordination bonding modes: 1,2-bidentate-3-monodentate and 1,2-bidentate-4-monodentate in complexes 1 and 3, respectively. In complex 2, two alternative bonding modes were detected: μ2-bridging 1,2-,2,3-bis(bidentate) and the new μ3-bridging mode 1,2-(bidentate)-3,5-bis(monodentate). The magnetic susceptibilities of the complexes were investigated at variable temperatures, and all reveal weak to very weak antiferromagnetic coupling.

Three polynuclear Cu(II) complexes bridged by croconato ligands were structurally and magnetically characterized. In these complexes, the bridged croconate dianion displays different bonding modes: 1,2-bidentate-3-monodentate, 1,2-bidentate-4-monodentate, 1,2-,2,3-bis(bidentate) and 1,2-(bidentate)-3,5-bis(monodentate).Figure optionsDownload as PowerPoint slideHighlights
► Three croconato-bridged-Cu(II) complexes were synthesized and structurally characterized.
► Different coordination bonding modes are reported for the bridged croconato ligands.
► A new bridged croconato bonding mode: μ3-1,2-(bidentate)-3,5-bis(monodentate) was detected.
► The complexes exhibit weak antiferromagnetic coupling.